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Lagrangian modelling of phytoplankton coexistence
Daniela Cianelli, Luciana Sabia, Maurizio Ribera dAlcalą, Enrico Zambianchi
Universitą Parthenope, Napoli
daniela.cianelli@uniparthenope.it(Abstract received 04/30/2005 for session A)
ABSTRACT
In the aquatic ecosystem processes controlling the phytoplankton growth are non linear; physical, chemical and biological factors, including resource availability, fluctuate both in time and space. The main resources for which phytoplankton species compete are not homogeneously distributed in the water column because of the spatial and temporal variability of turbulent mixing and the concurrent biological response. A dynamical description of light and nutrient supply is a prerequisite for the understanding of competition between phytoplankton species. On this basis, we have devised an Individual Based Model to investigate coexistence of two phytoplankton species in realistic turbulent conditions. We consider turbulent mixing as an additional factor determining the outcome of phytoplankton species competition. The model combines the availability of light and nutrients in the water column with the distribution of the different species determined by a realistic turbulent flow field. The two investigated phytoplankton species are characterized by different photophysiological behaviours and interact only through shading and turbulent mixing rate; the latter is simulated introducing measured values of vertical eddy diffusivity. Using the Lagrangian approach, the dynamics of the two phytoplankton populations is analyzed in terms of the unique temporal and spatial history of individual organisms and of the effect of realistic resource fluctuations upon them. Results suggest that turbulent conditions may induce different photosynthetic responses and adaptive strategies and have a major impact on the species composition during a phytoplankton bloom.
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2005 LAPCOD Meeting, Lerici, Italy, June 13-17, 2005